es7與es8

求冪運算符

let a = 7 ** 12
let b = 2 ** 7
console.log(a === Math.pow(7,12)) // true
console.log(b === Math.pow(2,7)) // true

//

let a = 7
a **= 12
let b = 2
b **= 7
console.log(a === Math.pow(7,12)) // true
console.log(b === Math.pow(2,7)) // true

另外一種寫法

let a = 7
a **= 12
let b = 2
b **= 7
console.log(a === Math.pow(7,12)) // true
console.log(b === Math.pow(2,7)) // true

includes方法

//包含數組裏的數，打印true。
//不包含數組裏的數，則打印false。
var aa=[1,2,3];
console.log(aa.includes(5));//false
console.log(aa.includes(3));//true

字符填充函數padStart 和 padEnd

padStart()

console.log('react'.padStart(10).length)         // "       react" is 10
console.log('backbone'.padStart(10).length)         // "  backbone" is 10

padEnd

console.log('react'.padEnd(10, ':-)'))         // "react:-):-" is 10
console.log('backbone'.padEnd(10, '*'))         // "backbone**" is 10